Single element print head



Sept. 1, 1959 G. A. WALKER 2,902,132

SINGLE ELEMENT PRINT HEAD Filed Dee. 30, 1955 7 all! 1 a, my 2 r mvENToRGEORGE A. WALKER f ha mum-n4 ATTORNEY United States Patent C SIN GLEVELEMENT PRINT George' A. Walker, Millbrook, N.Y., assignor` toInternational Business Machines Corporation, New York, N.Y., acorporation of New York Application December 30', 1955, Serial No.S56-,514

' Claims. (Cl.19752) This invention relates to printing elements andmore particularly to an improved support and driving mechanism for asingle element printing head.

Incopending application Serial' No. 547,482, led November 17, 1955 onbehalf of L. E. Palmer, et al. the complete details of a single elementtypewriter aref given including the means for selectingy the characteron a single element sphericalv head which is to be printed. In stillanother copending application Serial No'. 547,481, tiled November 1,7,1955 on behalf of l. E. Hickerson, et al., the details of one embodimentofthe driving mechanism for a1 single element spherical printing headare given.

One of the main problems in dealing with" single element spherical'printing heads is that since the characters are arranged. in rows ofdilerent' circumference (depending on` the location of. the row withrespect to a plane through the equator ofthe sphere)" a compensationfactor is' required.. That is, unless the tilting. takes place in aplane at right angles to the tiltI axis, then rotation is imparted 'tothehead` during tilting. This rotation during tilt (unless tilt' is atright angles to tilt axis) causes a bind in the drive mechanism, or elsea displacement of the character relati'veto a longitudinal' line. Tocompensate for this` condi tion, a` double universal-joint was employedin one embodiment of drive as shown in copending application Serial No.547,481, referred to hereinbefore,.and it is to compensate for thiscondition that the improved driving mechanism of" this invention hasbeen provided. Therefore it is Aas first object' of this invention.' toprov-ide an improved single'A elementv driving mechanism wherein theproblem 4of the: compensation factor has been eliminated.

It is stillf a further object of this invention t'o provide an'improved! drivingmechanism for ay single element printing head.

notherproblemwiththe single element spherical printing li'eadf is to'produce a uniform density of printingy irrespective of the characterbeing printed and accordingly, it is a still further objectl of thisinventioni to improve printing uniformity by providing' an improved'driving mechanismfor a single element spherical printing head wherein ananvil is provided behind the character that is being printedt is ast-ill further obie'ct of this invention to provide anint-iproved2driving'y mechanismv for asingle' element spherical printing head1wherein the problem of the compensation factor has been eliminated andwherein` an anvil is automatically provided behind the character which'vis being printed' therebyv improving the: printing unformity.

Another problem with respect to single element printing heads: is thecorrect registra-tion of. the character with. the printing position.`InsomeY previous embodiments it was necessary to provide detent meanswithin aspherical head ltoassure the correct. registration of thecharacter with a printing position, and accordingly, it is a stillfurther object of this invention to provide. an. improved drivingmechanism wherein theneed for a deten-t` mechanism with,- in thespherical head has been eliminated.

ICC

which has been contemplated, of' applying that principle.

InL the drawings:

Fig. l is a vertical section taken through the center of theprint headto show its driving mechanism.

Fig. 2 is a sectional view along plane 2-2 of'Fig. 3L in direction ofarrows.

Fig. 3 is a plan section taken along plane 3-3 of Fig. 1 in thedirection of the arrows.

Fig. 4 is an auxiliary view of a portion of the tilting mechanism.

Fig. 5 is a side elevation of bearing support.

Fig. 6 is a side elevation of tilt detent.

Briey, this invention relates to an improved mechanism for turning andtilting a single element spherical printing head in such a manner thatthe inner periphery ofthe print head is positively driven at only onepoint at a time, while the actual engaging point is stepped from pointto point along the inner periphery of the print head. Actually, theinner periphery of the print head is equipped with longitudinal. groves,and in this manner, the tilting ofthe print head relative to the drivingmeans takes place along a longitudinal line so that the compensation.factor is not involved..

Description` With reference to the drawings, and particularly Fig. l, aprinting mechanism 1 is shown supported in a rocker 3 which in. turn' issupported (in a manner not shown but described in application Serial No.547,482) for rocking movement into and out of printing position. It willbe understood that the printing mechanism is equipped with a singleelement spherical' printing head 4' having characters arranged in. rowsand columns on its spherical surface. Accordingly, provision must hemade for rotating and tilting the printing head so that a selectedcharacter will be indexed into a single printing position.

As described in U.S`. application, Serial No. 547,482, a selectingmechanism is provided for exerting a force simultaneously on a turn wire2 and a tilt wire 5. The wires 2` and 5 respectively are attached to arotation or turn pulley 6 and a tilt pulley 7, and the manipulation ofthese pulleys indexes a selected character into printing position.

Rotation Turn pulley 6 is connected via some positivel drive means, forexample, a pin 6a, to a shaft 8 which is supported for rotation relativeto rocker 3 by means of suitable bushings. Shaft 8 is equipped at: itsupper end' with a splined portion 12 which is engageable for positivedrive with a complementary splined element 14 in a pin barrel 16,

The pin barrel 16 is somewhat in the shape of an inverted bell having anannular ring 17 and a turned down lipV 18. The ring 17 andv lip 18 areperforated in a horizontal plane. along radial lines to provide bearingguides 20 for a plurality of drive pins 22.

With reference to Fig. 3', it can be seen that the pins 22v in passingthrough the guides 20 form pie shaped sections, and the guides are soshaped as` to permit the pins to slide radially inand out along radiallines.

Each pin 22 is further equipped with a groove. 24

which rides on a ring cam 26. The ring cam 26 is V2,902,132 M fsupported in rocker 3. The ring cam 26 has a single lobe 28 which is sopositioned that the major radius is directly in line with a printposition 3i) shown located on a platen 32 (Fig. 3).

With the mechanism above described it can be appreciated then that asthe pins 22 are rotated in a common plane about the axis of shaft 8, andtherefore relative to the stationary ring cam 26, the inter-engagementof the groove 24 and the ring cam 26 will drive the pins radially in andout as they pass print position 3i?. For example as the pins are movedcounterclockwise as viewed in Fig. 3 from nine oclock past printposition 39 towards three oclock, the pins are first gradually advancedradially outwardly so that at the print position 36 each pin in turn isat its maximum radial distance from the center of shaft 8, and then thepin is gradually withdrawn.

The single element spherical print head 4, as generally described in thecopending applications, Serial Numbers 547,481 and 547,482, is a hollowtruncated plastic sphere with the characters of a type font arranged onit in rings and columns. The print head 4 of the present invention isfurther provided with a plurality of internal grooves 36 (equal innumber to the pins 22) which are in the form of longitudinal lineshaving their greatest inter- `distance along the equator. The print head4 is further equipped with a central stub 3S which provides a ballsocket 40 engageable with a ball 42 located on the end of shaft 8. Thearrangement of parts is such that the ball 42 is directly at the centerof the print head 4 when it is assembled on the printing mechanism l.The ball socket 40, in view of the resilient qualities of the plasticprint head, can be sprung into and out of engagement with the ball 42thereby providing a releasable bearing support at the exact center ofthe spherical print head 4. ln view of the supporting means, the printhead 4 is concentric with respect to the axis of shaft 8, and it can beappreciated therefore, that as the pins are driven radially outwardly,each will sequentially engage its corresponding groove 36 and therebyprovide the positive driving means for rotating the print head about theaxis of shaft 8 in response to rotation of shaft t5.

Furthermore, the shape of the radially outer ends of the pins 22 iscomplementary to the shape of the grove 36 and accordingly, the pin 22at printing position 30 provides a positive interconnection with minimumplay between shaft 8 and print head 4. Accordingly, thisinter-engagement of the drive pin 22 at print position 30 with the printhead 4 serves the dual function of eliminating the need for an internaldetent arrangement for the print head 4 and also of providing an anvildirectly behind the character which is being printed thereby improvingthe uniformity of print density.

Compensation factor With the arrangement of the drive pins 22 and theinternal grooves 36 of the print head 4 as shown in Fig. 3, it can beseen that while the pin 22 at print position 30 is in positive drivingrelation with the print head, the pins on either side of the printposition are in partial driving relation with the print head, andaccordingly, some relative play between the drive pins and the printhead 4 is permissible at all points except print position, and since thegroove 36 at print position 30 lies in a plane perpendicular to the tiltaxis there will be no binding of the drive mechanism if the head istilted at the same time that it is being rotated about the axis of shaft8.

Tilt control carries a gear sector 56. Actually, the radial arm 54extends through a cut away slot in the support portion of the ring cam26 so that the arm can be rotated (through approximately 60) relative tothe ring cam 26.

In order to tilt print head 4, yoke 27 is provided with a pair of arms60, 62 which extend up beyond a horizontal plane passing through thecenter of ball 42. The arms 60, 62 in turn, are provided with halfbearings 64, 66 respectively, engageable with trunnions 68, 79respectively. As shown in Fig. 5, the trunnion 68 is held in engagementwith the half bearing 64 by means of a spring 72 while a correspondingspring 74 is provided on arm 62 to hold trunnion 70 in engagement withhalf bearing 66. It will be noted that the half bearings 64 and 66 areso shaped that during a print stroke the force of the print stroke istransmitted (as later described) to the arms 60 and 62 of the yoke 27without any tendency of the trunnions being lifted out of the halfbearings. l v The trunnions 68, 70, in turn, are riveted or otherwisesecured to a cradle 76 which is substantially of inverted U-shape andwhich acts to tilt print head 4 about ball 42. More specifically, oneleg 78 of the cradle 76 is equipped with a removable gear sector 80which is connected by means of a set screw 82 in such a manner that anadjustment can be made between sector 80 and the corresponding gearsector 56 to eliminate any gear tooth back lash. The opposite leg 84 ofthe cradle 76 is equipped with a plurality of notches or ball sockets 86(see Fig. 6 also), with one notch being provided for each row of type onthe print head 4. The yoke 27, in turn, is equipped with a ball detent88 of conventional type which is spring biased into engagement with onenotch 86 at a time. This arrangement insures the proper alignment of acorresponding row of type in printing position.

The cradle 76 is further provided with a center bearing stud 90 which isengageable with a complementary bore 92 in the center stud 38 of theprinting head 4. Accordingly, through the inter-engagement of thebearing stud 9i) with the bore 92 and the ball socket 40 with the ball42, a sturdy support is provided for the print head 4 thereby preventingtwisting of the print head during a. print blow.

Interchangeable print head It can be appreciated that in some instancesit is desirable to change a type font to accommodate a variation inprint conditions. With the structure described, it is a simple matter toremove one print head 4 and replace it with another. More specifically,the springs 72 and 74 on yoke arms 60, 62 respectively are rst raisedout of engagement with the trunnions 68, 70 respectively and then thecradle 76 can be lifted away from the yoke 58 with the bearing stud 90being lifted out of the corresponding bore 92. Then the print head 4 canbe snappedaway from the ball 42 and replaced with one having a differenttype font. The cradle 76 is again assembled in the yoke 27 and theprinting mechanism 1 is again ready for operation.

It has been found that through the use of this improved print head drivemechanism an accurate turning and tilting mechanism is provided for asingle element spherical printing head wherein the problem of thecompensation factor has been removed, and furthermore, in view of thefact that, in the form of drive pin 22, an anvil is positioned behindthe character being printed, the printed product has a very uniformcolor density.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the artwithout departing from the spirit of the invention. It is the intentiontherefore, to be limited only as indicated by the scope of the followingclaims.

What is claimed is:

l. An improved support and' drive mechanism for a single elementspherical print head comprising a rotatable supporting shaft, meansmounting the spherical center of said print head for universal movementrelative to one end of said shaft, means interconnecting said print headfor rotation with said shaft, said interconnecting means comprising aplurality of drive pins angularly positioned about said spherical centerand movable radially relative thereto, means connecting said d'rive pinsfor rotation with said shaft, and stationary means engaging said pinsfor effecting, on rotation of said shaft, sequential radial movement ofsaid drive pins relative to said shaft and into engagement with saidprint head to effect a driving of the latter with said shaft.

2. An improved support and d'rive mechanism for a single elementspherical print head comprising a supporting shaft, means mounting thespherical center of said print head for universal movement relative -toone end of said shaft, and means interconnecting said print head andsaid shaft comprising a plurality of drive pins radially positionedrelative to said spherical center, means mounting said drive pins forrotation with said shaft, and stationery means engaging said pins foreffecting radial movement of said drive pins relative to said shaft, andinto driving engagement with said print head, said radially moving meansbeing so arranged that only one pin at a time is in full drivingengagement with said print head.

3. An improved support and drive mechanism for a single elementspherical printing head comprising a supporting shaft, means mountingthe spherical center of said print head for universal movement relativeto one end of said shaft, and means turning said print head about theaxis of said shaft comprising a plurality of drive pins mounted in aplane including the spherical center of said print head, a plurality ofgrooves on the inner surface of said print head, and means responsive tothe turning of said shaft for radially moving one of said pins at a timesequentially into complete driving engagement with its correspondinggroove thereby rotating said print head.

4. An improved support and drive mechanism for a single elementspherical plinting head comprising a supporting shaft, means mountingthe spherical center of said print head for universal movement relativeto one end of said shaft, and means turning said print head about theaxis of said shaft comprising a plurality of drive pins mounted in aplane including the spherical center of said print head, a plurality oflongitudinal grooves equal in number to said pins on the inner surfaceof said print head, and means responsive to the turning of said shaftfor radially moving one of said pins at a time sequentially intocomplete driving engagement with its corresponding groove therebyrotating said print head.

5. A mechanism in accordance with claim 3 wherein said radial movingmeans `for said drive pins comprises a ring cam having a single highdwell at a predetermined point of engagement between said pins and saidprint head, and means interconnecting said pins and said ring cam.

6. A mechanism in accordance with claim 3 wherein said radial movingmeans for said drive pins` comprises a ring cam having a single highdwell at a predetermined point of engagement between said pins and saidprint head, each of said pins having a notch engageable with said ringcam, and means for turning said pins about the axis of said shaft andthereby driving said pins radially into engagement with said print headto turn the latter about the axis of said shaft.

7. An improved support and drive mechanism for a 6 single element printhead comprising a supporting shaft, means mounting the spherical centerof said print head for universal movement relative to one end of saidshaft, and single point drive means for turning said print head aboutthe axis of said shaft comprising a plurality of drive pins, meansmounting said drive pins in a common plane including the sphericalcenter of said element for movement about the axis of said shaft andlfor movement radially of said shaft, pin drive means comprising aflxedly mounted ring cam concentric with said drive pin mounting means,said ring cam having a single lobe proximate to a predetermined point ofengagement with said type head, and means interconnecting said ring camand said pins whereby -the rotation of said pins drives said pinsradially relative to said shaft in conformity with the shape of saidring cam.

8. An improved support and drive mechanism for a single elementspherical print head comprising a support shaft, means mounting saidprint head -for universal movement relative to one end of said shaft,additional means supporting said print head for tilting movement about atilt axis perpendicular to the axis of said shaft and changing singlepoint drive means for turning said print head relative to said shaftcomprising means supporting a plurality of drive pins for rotation aboutthe axis of and for radial movement relative to said shaft, a pluralityof longitudinal grooves in the inner periphery of said spherical printhead, and means providing for the inter-engagement of one of said drivepins and a corresponding longitudinal groove at a point lying in a planeperpendicular to the tilt axis of said spherical print head, comprisinga ring cam ixedly mounted concentrically of said shaft for engagementwith said drive pins, said ring cam having a high dwell point in a planeperpendicular to the tilt axis of said print head, and means moving saidpins relative to said ring cam whereupon as said drive pins are turnedrelative to said ring cam they are moved radially outwardly intoengagement with their corresponding groove by the high dwell point ofsaid ring cam.

9. An improved support and drive mechanism for a single elementspherical print head comprising a support shaft, means mounting thespherical center of said print head for universal movement relative tosaid support shaft, tilting means for tilting said print head about afixed tilt axis, and varying turn means interconnecting said print headand said supporting shaft at a point lying in the plane perpendicular tosaid tilt axis, comprising a plurality of drive pins, means mounting thesame in a plane including the spherical center of said print head, anumber of longitudinal grooves in the inner wall of said print headcorresponding in number to said pins, and means responsive to theturning of said shaft for turning said drive pins about the axis of saidshaft and sequentially driving said pins radially into engagement withtheir corresponding grooves in said print head at a point lying in theplane perpendicular to said tilt axis.

l0. A mechanism in accordance with claim 9 wherein said radial drivemeans comprises a ring cam fixed relative to said support shaft andhaving a single lobe located in a radial line through the center of saidshaft and perpendicular to said tilt axis, and means interconnectingsaid drive pins and said ring cam so that the turning of said pins aboutthe axis of said shaft drives them sequentially into engagement withtheir corresponding grooves proximate to the lobe of said ring cam.

References Cited in the ile of this patent UNITED STATES PATENTS 696,833Maxwell Apr. 1, 1902

